[disclaimer]This is just my personal experience and why i do this, i dont know if this is the reason for other intps or not[/disclaimer]
Its not usually complexing simple things in my personal experience. Its about looking under the surface of the "simple" thing and only on the surface that thing is looking simple. But when looking on principles on how that simple thing is working and why is it what it is, it usually is more complex thing than what it seems to be on the surface. Since most people only see the surface of it, it will look simple thing to them and they see that intp is making it more complex than what it really is.
Kinda same thing happens when intp is simplifying a complicated thing. The thing just seems complicated on the surface, but when you dig deeper into principles of it, it usually is more simple than what it seems to be on the surface, but most people only see the surface of things..
At times some things might be simple under the surface also and when intp tries to look under the surface to see if there actually is some complicated things hiding there, they need to handle that simple thing as if it was more complex than it actually is, until they realize that it is simple under the surface also. When this happens intp is actually making a simple thing more complex than what it actually is, but usually this isnt the case, because quite rarely things are as simple as they seem on the surface, but most people dont understand this, so they just see intp making simple things more complex than they actually are every time they look under the surface, not matter if it actually is more complex or not.
Can other intps relate with this?